1. Technical Field
The present invention relates to a mass storage device such as a hard disk drive, and more particularly to a method for improving a read/write performance on a track having a re-allocation sector in a hard disk drive.
2. Related Art
Hard disk drive (HDD) is widely used as an auxiliary memory device of a computer system because it can access a large amount of data at high speed. Typically, the hard disk drives (HDD) include one or more magnetic disks defining a multiplicity of concentric data tracks. Each data track is divided into alternating data and servo sectors with intersector gaps therebetween. The data sector are used for the storage of main data or user information. The servo sectors are used for the storage of control data such as automatic gain control data, track addresses and tracking servo patterns for use in positioning a head. Magnetic disk drives having high data density generally rely upon servo control systems for moving a selected transducer (head) from a departure track to a destination track location when data information is written or read from the disk.
A typical data sector includes a plurality of identification (ID) regions, data regions and PAD (postamble data) regions serving as intersector gaps therebetween. The servo sector includes a preamble, a servo address mark SAM, a gray code, bursts A, B, C, and D, and a PAD. The preamble, a so-called servo synchronization, provides a clock synchronization during reading the servo information and provides a gap in front of the servo sector to indicate the servo sector. The servo address mark SAM indicates a beginning of the servo sector to provide a synchronization for reading the following gray code. That is, the servo address mark SAM provides a reference point for generating various timing pulses regarding the servo control. The gray code provides track information, i.e., the track number. The bursts A, B, C and D provide a position error signal PES required for the track seek and the track following. The PAD provides a transition margin as a data sector in the servo sector.
When there is a defective sector, the hard disk drive re-allocates a spare sector prepared in the disk for the defect sector. Thereafter, upon receipt of an access command for accessing the defective sectors in a defective track, the hard disk drive searches a defective list in a maintenance area of the disk to check whether the track has a defective sector. If the track has a defective sector, the hard disk drive will access up to a sector preceding the defective and search the re-allocation sector that has replaced the defective sector, to access the re-allocation sector. Thereafter, the hard disk drive moves to the original track to access the next sectors. Various techniques for allocation replacement of defective sectors in a hard disk drive can be found, for example, in U.S. Pat. No. 4,405,952 for Apparatus For Detecting Faulty Sectors And For Allocating Replacement Sectors In A Magnetic Disc Memory issued to Slakmon, U.S. Pat. No. 4,631,723 for Mass Storage Disk Drive defectiveive Media Handling issued to Rathbun et al., U.S. Pat. No. 4,706,136 for Method For Controlling A Magnetic Disk Memory issued to Wentzel et al., U.S. Pat. No. 4,746,998 for Method For Mapping Around defectiveive Sectors In A Disc Drive issued to Robinson et al., U.S. Pat. No. 4,914,530 for Media defective Management Within Disk Drive Sector Format issued to Graham et al., U.S. Pat. No. 5,075,804 for Management Of defective Areas In Recording Media issued to Deyring, U.S. Pat. No. 5,235,585 for Reassigning defectiveive Sectors On A Disk issued to Bish et al., U.S. Pat. No. 5,271,018 for Method And Apparatus For Media defective Management And Media Addressing issued to Chan, and U.S. Pat. No. 5,285,436 for Method Of Avoiding Medium defectives In Record/Reproduce Apparatus issued to Moribe.
Generally, the contemporary hard disk drive must search for defective sectors every time in order to access the re-allocation sectors corresponding to the defective sectors, so that a data transmission of a host computer may be lowered, which results into a deterioration of the drive performance.